Yellow fever virus (YFV) 17D is a live, attenuated vaccine that has been used in humans for over 60 years. More than 300 million people have received the vaccine, with an outstanding record of safety and efficacy. After a single dose, neutralizing antibodies appear in nearly 100% of vaccines within 10 days. Immunity is extremely durable, and may be life long. YFV-17D is very immunogenic in humans, with a 90% immunizing dose of only 5-20 plaque-forming units of virus.
Yellow fever virus is the prototype member of a family of viruses, the flavivirus. Virions are spherical and about 40-50 nm in diameter. The nucleocapsid has icosahedral symmetry, contains the RNA genome, and a single core protein, and is surrounded by a lipid bilayer envelope. The viral genome is composed of a single-stranded RNA of positive polarity. The viral genome contains a single, long open reading frame that encodes 10 viral proteins.
Flaviviruses have been developed as vehicles for delivery of foreign proteins to a mammalian host for the purpose of generating an immune response to the foreign protein(s). Bonaldo et al. (2000) Mem. Inst. Oswaldo Cruz 95:215-223. In recombinant flaviviruses described to date, a nucleic acid molecule encoding the foreign protein is inserted into a region encoding viral proteins. Such recombinant viruses encode a polyprotein precursor in which the foreign protein is inserted, and which must then be cleaved out. A potential drawback to such recombinant viruses is that, because the polyprotein precursor includes an exogenous polypeptide, the viral proteins may be misfolded and therefore may not function normally.
There is a need in the art for improved recombinant viruses that are useful in delivering foreign proteins to a mammalian host. The present invention addresses this need.
Literature
WO 93/11250; Julius et al. (2000) BioTechniques 28:702-708; Pizzato et al. (1998) Gene Therapy 5:1003-1007; Lopez de Quinto et al. (1998) Gene 217:51-56; WO 00/65034; WO 00/16800; U.S. Pat. Nos. 5,854,037; 5,935,819; Bonaldo et al. (2000) Mem. Inst. Oswaldo Cruz 95:215-223.